A method and apparatus for determining a reflectance, of at least a portion of a target object, in at least one selected wavelength range of electromagnetic (EM) radiation are disclosed. The method comprises, for each selected wavelength range, providing a digital image including at least one target object and a plurality of reference objects, each reference object having respective non-identical predetermined reflectance characteristics, with a digital camera arrangement that provides output image data that comprises digital numbers that are responsive to radiation, in only a selected wavelength range, incident at a sensing plane of the digital camera arrangement. A relationship between a first set of the digital numbers is determined and a first set of the respective predetermined reflectance characteristics of the reference objects. Responsive to the relationship, a further set of digital numbers is transformed to allocate a value of reflectance for each of the digital numbers in the further set. For at least a portion of the target object, a corresponding first group of allocated values of reflectance is determined and responsive to the first group of allocated values, determining a reflectance of the portion of the target object.
Legal claims defining the scope of protection, as filed with the USPTO.
4. The method as claimed in claim 2, wherein the index of reflectance is a Normalised Differenced Vegetation Index (NDVI) or a Photochemical Reflectance Index (PRI).
6. The method as claimed in claim 1 wherein a predetermined reflectance characteristic of a reference object is a reflectance, for a selected wavelength range, of the reference object.
7. The method as claimed in claim 1 wherein each portion of a target object comprises at least one region of interest.
8. The method as claimed in claim 1 wherein a selected wavelength range of electromagnetic (EM) radiation is selected from a wavelength range of visible red light or from a wavelength range of near-infrared (NIR) light.
12. The apparatus as claimed in claim 9, wherein the digital camera arrangement comprises at least one digital camera and optionally a Raspberry Pi Camera Module, for example a Raspberry Pi Camera Module V2, and/or a Raspberry Pi NoIR Camera Module, for example a Raspberry Pi Camera Module NoIR V2.
13. The apparatus as claimed in claim 9, wherein the digital camera arrangement comprises a plurality of electromagnetic radiation filters.
14. The apparatus as claimed in claim 13 wherein at least one of the plurality of electromagnetic radiation filters comprises a near infrared (NIR) light filter and at least of one of the plurality of electromagnetic radiation filters comprises a blue optical filter.
15. The apparatus as claimed in claim 9 wherein the digital camera arrangement comprises a single-board computer.
16. The apparatus as claimed in claim 15 wherein the single-board computer is a Raspberry Pi computer and optionally is a Raspberry Pi 3 or a Raspberry Pi 4.
17. The apparatus as claimed in claim 9 wherein the digital camera arrangement comprises a part of a handheld device.
18. The apparatus as claimed in claim 9, wherein the digital camera arrangement is mounted to an unmanned aerial vehicle (UAV), optionally an unmanned quadcopter or a drone, or a manned aerial vehicle, optionally an aeroplane or a helicopter, or a piece of agricultural equipment, optionally a tractor or a harvester.
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November 27, 2020
October 8, 2024
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